The border area joining California and Mexico (San Diego and Imperial counties) is a region of dynamic change, characterized by population growth rivaling that of the world's fastest growing and most impoverished nations. The rapid population growth in this region is occurring in a context that includes substantial alterations to the region's economic and environmental conditions. Yet, little is known whether these changes have resulted in an adverse impact on public health. Many of these population and environmental changes have been occurring in two border California counties, San Diego and Imperial, which are the focus of this study. Health effects which may occur as a result of population or environmental changes may not be detectable in traditional demographic/health indices, such as mortality, but require more sensitive indicators, such as sentinel health events (SHEs). SHEs are preventable illnesses or diseases (such as childhood respiratory diseases, skin cancer, leukemia, and low birthweight) that serve as early warning that the public health is being threatened by a deterioration of its environmental infrastructure. This study will document trends in SHEs in the border area that will be representative and specific to changes in population/environmental patterns. These data are available in several health-related databases maintained by the State of California. Over the course of the last decade, computerized geographic information systems (GIS) and detailed geo-coded databases on population characteristics and environmental quality have been developed, which have special application to studying these changes in the border area. By tracking and documenting changes in demographic, environmental, and health measures overt the last 15 years in San Diego and Imperial counties and by creating a linked database, the proposed study will test the following hypotheses: * Are indices of population growth associated with measures of environmental degradation in the border area? * Are measures of environmental degradation associated with measurable increases in SHEs? * Can one or more SHEs be used as a reliable indicator of changes in population and/or environmental conditions?